To contact one of our “Forage for Profit” team, call the Seed Office on 01769 576232
or Graham Ragg on 07798 583667 or email info@molevalleyfarmers.com.

The relationship between soil and minerals in forage

A down-to-earth explanation

by John Lawrence, Mineral Supplements Technical Manager

It is important to understand that whilst any minerals found in forages (or any crop for that matter) will originate from the soil in which they are growing, it does not follow that if the soil is high in a particular element that the forage will be too!

The reason for this is that the uptake of each element is dictated by soil pH with different elements being taken up at different pH levels. Uptake is also affected by any antagonism between the elements. A classic example of this would be molybdenum, well known for its antagonistic effect on copper availability to cattle in particular. This is where elevated molybdenum levels in the forage can lead to a “lock-up” of copper in the rumen. However unless the soil pH is very high (pH7 or above) a high level of molybdenum in the soil will have little if any effect on the level of molybdenum in the forage!

Fortunately the uptake of copper and most of the beneficial elements is greater at levels below pH 7 (6-6.5) But if the soil is low in a particular element then the forage will also be low. It should also be noted that the level of minerals and trace elements taken up by the plant is largely dependant on the amount of time the crop has been growing. Short term crops such as maize or whole crop would contain very low levels of minerals compared to say silage from a long term ley.

TIP: To aid management of the crop test the soil To aid management of livestock, test the forage

Forage mineral analysis

This is a key tool in understanding the “typical” mineral footprint of your farm, which may well be very different to that of your neighbour’s. This can be due to a number of factors including intensity of management, fertilizer practice, frequency of cropping or harvesting, geographical or topographical reasons and soil pH.

A forage mineral analysis carried out approximately every 4-5 years can be used in conjunction with your ration and herd performance details to carry out a Nutri-LINK diet/mineral check. We can then formulate the correct mineral supplementation program to suit your requirements.

Minerals for the grazing season

Firstly and most importantly, remember that whilst the type of mineral required to balance a grass based diet may differ from that used for winter rations, the mineral requirement is still there. Arguably it is more important as you are more in control of the animals’ nutrition when housed. Grass is notably variable as a feed and for minerals. As shown by the chart, grass is a poor provider of trace elements.

Vitamin levels in grass can also vary widely depending on the season and in particular the amount of sunshine.

Udder health

Elevated somatic cell counts and / or mastitis can be an issue during the summer months. This may be attributed to the weather, soil conditions or nutrition. The cows may be receiving less minerals than they should – maybe for practical reasons. However, there are essential trace elements and vitamins which are responsible for the immune system function, especially zinc, selenium and vitamin E.

The chart on this page shows that grass is a poor source of zinc and selenium even in good conditions, but in a wet summer with low sunlight, vitamin E is also likely to be low. To this end, ensure that minerals are supplied to your herd during the grazing season and if udder health is a problem to you, talk to us about the option to adjust your mineral or to include Bioplex zinc and Sel- Plex selenium.

Magnesium

We are all aware that grass can be deficient in magnesium highlighted by the prevalence of grass staggers (hypomagnesaemia). As we know, the risk is greatest at turnout and during an autumn grass flush; precipitated by stressful conditions such as cold wet or stormy weather and especially where potash or slurry have been recently applied to grazing land. In these circumstances dairy and beef cows in particular require daily magnesium supplementation.

Remember that if you are a cake feeder, only animals receiving the recommended rate will receive adequate magnesium, so always provide a secondary source such as high magnesium minerals, buckets or blocks or you may prefer to add magnesium chloride to the drinking water. In any event do not rely on one source of supply only.